Cameras serve as image capture devices, taking pictures of an ambient scene through an objective lens. For example, a photographic still camera stores an image, either photoelectronically into memory or photochemically onto a filmstrip, when an image capture button, such as a shutter button, is fully depressed. In a still camera, pressing the shutter button causes a shutter to be tripped, which permits light from the scene to pass through the objective lens and fall onto a photodiode array or film strip located at a focal plane of the lens. A video camera or movie camera captures a sequence of images that, when played back, presents the illusion of motion.
A camera user typically looks through a camera viewfinder to determine which portion of the scene is within the camera's field of view. At times, such as under low light conditions or in a crowded scene, it can be difficult to judge the portion of the scene which is in the camera's field of view. At other times, such as when tracking fast moving objects in the scene or when picture taking discretion is desired, it might be desirable to compose a scene without looking through the viewfinder at all. However, not using the viewfinder to compose a scene risks cutting off a part of the scene whose image the camera user would like to capture.
U.S. Pat. No. 5,059,019 (the '019 patent) provides a solution to the problems mentioned in the previous paragraph. The '019 patent discloses a movie camera having a laser framefinder. The laser framefinder generates a laser beam which is scanned about the periphery of a portion of a scene that is in the camera's field of view. The result is four solid appearing lines which frame a portion of the scene. As such, the camera operator can discern the portion of the scene being captured by the camera by simply observing where the laser light frame falls on the scene.
Although the disclosure of the '019 patent permits easier scene composition, there is no provision for varying the brightness of the laser light frame to account for the widely varying conditions under which the camera is used. For example, under bright ambient light conditions or when the camera-to scene distance is great, it can be difficult to see the laser frame and discern the portion of the scene about which the laser frame is located. Conversely, under dim ambient light conditions or when the camera-to scene distance is small, the laser frame can be too bright, distracting the camera operator and those people whose image is to be recorded.
Thus, it would be desirable to control the brightness of the emitted beam so that the laser frame is readily discernible to the camera user under a variety of conditions. Further, while it is important that the emitted beam should be sufficiently bright to be readily seen by the camera user, it also is important that the beam not be so extraordinarily bright that it distracts persons or animals in the scene.
From the discussion above, it should be apparent that there is a need for a camera with a framing aid that is visible under a variety of conditions. The present invention fulfills this need.